manual/include/midi-on-linux.html

<p>
  It is no longer necessary to use jackd as a backend for Ardour in Linux.
  In fact with the spread of LV2 plugins, almost all workflows in Ardour work
  well with the ALSA backend. When using the ALSA backend for Ardour, Ardour
  will see all MIDI ports that ALSA sees without any user setup. However, should jackd
  need to be used, the rest of this page is valid.
</p>

<p>
  The right approach for using MIDI on Linux depends on which version of JACK
  is in use. The world divides into:
</p>

<table class="dl">
  <tr><th>Systems using JACK 1, versions 0.124 or later</th>
  <td>On these systems, JACK must be started with the <code>-X alsa_midi</code>
  server argument. To support legacy control applications, the <code>-X
  seq</code> argument to the ALSA backend of JACK can also be used to get the
  exact same results.</td></tr>
  <tr><th>All others</th>
  <td>Using a2jmidid acts as a bridge between ALSA MIDI and JACK. The <code>-X seq</code>
  or <code>-X raw</code> arguments should <em>not</em> be used&mdash;the timing and
  performance of these options is unacceptable.</td></tr>
</table>

<h2>Using a2jmidid</h2>

<p>
  <dfn>a2jmidid</dfn> is an application that bridges between the system
  <abbr title="Musical Instrument Digital Interface">MIDI</abbr> ports and
  <abbr title="JACK Audio Connection Kit">JACK</abbr>.
</p>

<p>
  First it must be ensured that there is no ALSA sequencer support enabled in
  JACK. To check that, one must open QJackCtl's <kbd class="menu">Setup</kbd> window
  and set <kbd class="menu">Settings &gt; MIDI Driver</kbd> to <kbd
  class="input">none</kbd>, then uncheck the <kbd class="optoff">Misc &gt;
  Enable ALSA Sequencer support</kbd> option. The jack server must then be restarted
  before going on.
</p>

<h3>Checking for a2jmidid availability</h3>

<p>
  Next, it must be checked whether a2jmidid is already installed. This is done
  by starting the JACK server, then going to the command line and typing:
</p>

<kbd class="cmd lin">a2jmidid -e</kbd>

<p>
  If a2jmidid does not exist, it must be installed with the software manager of the
  Linux distribution in use until this command responds.
</p>

<h2>Checking available MIDI ports</h2>

<p>
  If JACK is correctly configured for MIDI, then the MIDI ports should appear
  in qjackctl under <kbd class="menu">Connections &gt; MIDI</kbd>.
</p>

<h3>Making it automatic</h3>

<p>
  Once it has been verified that the ports appear in JACK as expected, this can
  be made to happen whenever JACK is started:
</p>

<ul>
  <li>If a newer version of JACK 1 is in use, by just making sure the <code>-X
  alsa_midi</code> or <code>-X seq</code> options are enabled for whatever
  technique is being used to start JACK.</li>
  <li>For other versions of JACK, by adding <code>a2jmidid -e &amp;</code> as an
  "after start-up" script in the <kbd class="menu">Setup &gt; Options</kbd> tab
  of QJackCtl, so that it is started automatically whenever JACK is
  started.</li>
</ul>